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Every tech conference I've ever been to, and I've been to a lot, has had absolutely abysmal Wi-Fi and Internet access.

Sometimes it's the DHCP server running out of addresses. Sometimes the backhaul is clearly inadequate. Sometimes there's one router for a ballroom with 3000 people. But it's always SOMETHING. It never works.

What are some of the best practices for conference organizers? What questions should they ask the conference venue or ISP to know, in advance, if the Wi-Fi is going to work? What are the most common causes of crappy Wi-Fi at conferences? Are they avoidable, or is Wi-Fi simply not an adequate technology for large conferences?

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Come to DEFCON! (Although I left my netbook off...) –  Tom Hawtin - tackline Oct 9 '09 at 1:54
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Future DevDays might need to get in touch with the building manager and see if you can BYO networking equipment. A lot of additional headaches sure, but probably the only reasonable solution! –  Mark Henderson Oct 9 '09 at 2:44
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(cos you could totally use a few more rep) –  Mark Henderson Oct 9 '09 at 2:54
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@Joel: you should define terms. "Large conference" = 600 attendees, I would imagine. People seem to be harping on 3000 attendees, but that's not what you're REALLY asking, is it? Because 600 and 3000 require completely different solutions. –  Portman Oct 9 '09 at 19:55
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802.11 is not great a scaling, due the hidden node problems, so with lots of clients the physical mac layer collapses. frottle.sourceforge.net has some nice solutions. Also, it's a bit of hack , but some access points can be made to use channel 14, thus giving you almost 4 non-overlapping channels. at 2.4ghz if you plan you physical wireless layout properly, you can over lap your channels slightly –  The Unix Janitor Mar 20 '10 at 5:55

45 Answers 45

At linux.conf.au 2008 (Located in the lovely internet backwater that is Australia) we easily filled a 100Mbit pipe just with users over WiFi. (The bottleneck was a 100Mbit interface on our edge router, with some better planning we would have had 200-300 Mbit available).

Each attendee used ~250k/sec, probably >750k/sec as usually less then 1/3 were connected at any time.

In my day job I run educational networks, that bandwidth is more then many entire schools use here.

For a true heavy tech conference you really do need to budget that amount of bandwidth.

What was unexpected was that many attendees tried to mirror the conference video which was located office (In Canberra not Melbourne). Once we added a local mirror things improved a lot.

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Maybe you should get a cell in a box http://www.calzavara.it/lang/en/products/telecommunications/radio%5Fstation%5Fkit.html and provide attendees with wireless 3G USB sticks.

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This wouldn't work. That many people trying to use a single cell of a 3G network would overload the cell. –  Joel Spolsky Oct 11 '09 at 0:41

Not sure if it's been mentioned, but it's worth mentioning the problem of fake access points.

At Tech-Ed in Auckland this year there were at least 2 fake access points, supposedly set up with key loggers.

In fact one of the security speakers apparently had his laptop hacked right in the middle of a talk.

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Apparent figures from this years DEFCON: 270 rogue APs, 535 Man-in-the-Middle attacks, 200 DoS attacks, 750 wireless bridges, 2,090 AP MAC spoofing attempts. –  Tom Hawtin - tackline Oct 13 '09 at 0:38

This topic is definitely an issue that grows each day. With the growing number of IPhone, Android phones and other handhelds that use Wifi. Also with the growing importance of social meda to events (even non tech events). This is an issue that has to given more attention by conference managers and organizers.

I agree that most of the time Internet access is just an after thought. Even some high profile tech events I've worked or attended had major wifi issues.

So much great information on this thread....still digesting.

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There is something like fifteen channels of Wi-Fi now. 3 in the crappy and horrible 2.4 GHz band and 12 in the wonderful 5 GHz band. With all these channels a decent network can be built. This is something over 300 MHz to share. It is however horrible that the iPhone 3GS does not have a dual band 2.4/5 GHz Wi-Fi radio (I think some black berry's do). This is the only reason I have not purchased one.

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My company is the IS/IT geeks to IEEE, IETF, IGF, etc. So thanks goes out for those who say the networks, work.

Having a great network is not a want, it is a need. Members who attend events, tend to attend many events all over the globe. They are away from home offices and must do double duty by being a member of a group working on a standard and stay connected with the office as work must move forward.

I wish I could get all the work available, but that is not possible. The best recommendations I would give are:

1) References; require a possible vendor to produce references from similar or larger events with similar needs (Wi-Fi, Cyber cafe, audio video streaming, dictation, etc). You dont want to be teaching someone you are paying.

2) Billing; Your first event with a new vendor should have a detailed description of services with start end date and time, number of engineers onsite, response time for after meeting hours. You need to know the final bill before you engage the vendor.

3) Hardware; Enterprise hardware is a must. Working with a larger IT firm will make sure hardware stays currents as they will have enough clients to always afford upgrading to best of breed hardware.

4) Staffing; Not all IT geeks are created equal. Proper planning reduces the head count for onsite staff, also seen it, done it, made it a turn key product makes it so our typical meeting is staff at 1 geek to 250 attending members, now this number will be higher if audio and video streaming, or other special needs are requested. As an example IEEE 802 with 1300 attending members is staffed with 5 VeriLAN staff.

Contact VeriLAN http://www.verilan.com for additional information.

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I've attended a couple of Debconfs, and their wifi network just works.

Their equipment and software setup are detailed here:

No fancy cisco hardware, just hardware that runs OpenWRT well like Fonera devices.

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If you want to know how to create a good tech conference network, check out the network review from the 23rd Chaos Communication Congress in Berlin:

ftp://ftp.ccc.de/congress/23C3/video/23C3-1728-en-23c3%5Fnetwork%5Freview.m4v

If you don't have an hour left to watch this presentation, the short answer is: It will be a lot of work.

The Wifi setup is described at the end of the presentation (last 20 mins or so).

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The PyCon conferences (almost a 1000 attendees for the last two years) usually have pretty good wireless. The conference networking is done by a firm called tummy.com. You can read Sean's writeups on the last three year's networking:

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Joel, there are two parts to solving this problem: 1: Internet access at conferences should be a paid optional extra 2: Internet access should be provided via 3G USB modems

How about the idea of having a telco provide 3G modems to everyone at the conference? Each user pays a deposit for the modem which they get back when they hand it in at the end of the conference.

The assumption seems to be that conferences have an obligation to provide free wireless. Perhaps this assumption should be challenged.

Historically, the assumption was that airlines had to carry for free as much baggage as you could lug. Nowadays baggage is an optional extra that passengers must pay for.

Why should it be any different at conferences? When you buy your conference ticket you have the option of paying your refundable deposit for the 3G modem for use during the conference. Plenty of people already have wireless mobile Internet so they'll bring their own.

The problem is not "how to provide wireless access at conferences (at a reasonable cost)". The problem is "why do conference organisers assume that wireless should be free and not an optional extra"?

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I wrote a long article on why conference WiFi sucks and how to improve it. This article includes a Q&A with Tim Pozar.

http://www.muniwireless.com/2009/11/19/why-conference-wifi-sucks-and-how-to-improve-it/

Esme Vos

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Joel Spolsky wrote about this issue:

http://joelonsoftware.com/items/2009/10/08.html

James Mitchell

www.jmitchell.me

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The NANOG conference is targeted at the network engineers who run the Internet backbones. They have three conferences a year moving around North America and the wifi is almost always flawless. There is no more demanding audience than these network engineers many of whom are actually monitoring their own networks over the wifi in case problems arise during the conference. These are the 3rd level support guys who designed the networks and the buck stops in their mailbox/pager/cellphone.

Some of the people who have been involved in providing the conference wifi over the years have published details of what they do. http://seclists.org/nanog/2007/Feb/281 http://www.nanog.org/meetings/nanog38/presentations/kapela.pdf http://nanog.org/meetings/nanog39/presentations/abley-bof.pdf http://www.gossamer-threads.com/lists/nanog/users/95657

Some of it is planning, some of it is intimate understanding of the technology which is NOT JUST NETWORKING but involves lots of radios too. That's what leads them to put lots of APs around the edges of the room with the power cranked DOWN.

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High performance secure networking is not a plug-and-play kind of thing. For example:

You can eliminate a lot of peer-to-peer chatter yet still allow Internet access by partitioning your network up so that each client can only broadcast to itself and the router. I do this to help stop virus/worm propogation and snooping on shared drives for hotel and motel Internet users.

Instead of one class-C or class-B for everbody, you can chop up the address space into little 4 address chunks (/32 instead of /24). That gives you 64 subnets on a class C. Using the 172.27.0.0/16 range, you'd get 256*64 = 16,384 unique subnets. Each of those has its own router IP and broadcast address so your broadcasts are just between you and the router - they don't propogate beyond to the other clients - thus Windows doesn't discover other PCs with their network shares. Instead of 256 clients with:

IP 172.27.1.x netmask 255.255.255.0 gateway 172.27.1.254 and broadcast 172.27.1.255

you would get 64 clients like:

Client 1 : IP 172.27.1.1 gateway 172.27.1.2 netmask 255.255.255.252 gateway 172.27.1.2 broadcast 172.27.1.3

Client 2 : IP 172.27.1.5 gateway 172.27.1.6 netmask 255.255.255.252 gateway 172.27.1.6 broadcast 172.27.1.7

You do end up needing to write scripts to generate the configuration for dhcpd.conf and /etc/network/interfaces since there's an entry for each client. Also with this scheme, ifconfig will show you just how much traffic each client has used (up to 4 GB, after which the transferred bytes and received bytes counters reset).

... that's just messing about on the layer-3 stuff. Wired APs will be better than using WDS (easier set-up but halves your bandwidth or worse).

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Why is Wi-Fi so poor at tech conferences?

BitTorrent! That's why! Check out this blog post from MS TechEd network engineer that performed an analysis about what was screwing up the conference network.

At this year's TechEd they're planning to implement rate limiting, bandwidth quotas & deep packet inspection in an effort to stem the torrent tide.

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